The invention described herein arose in the course of, or under, Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California.
This invention relates to a process and apparatus for measuring the degree of polarization of a beam of polarized light and the angle of the major axis of the polarized beam. More particularly, this invention relates to a process and an apparatus for measuring such optical polarization properties of an optical point at a first point along an optical path and then adjusting compensating optics at a second point on the optical path to obtain identical optical measurements at this point.
When a beam of polarized light, such as a laser beam, is passed through various optics, such as lenses and mirrors, it is often desirable to analyze the light beam at a particular point in the optics system. Such an analysis would include the phase or degree of polarization of the light beam as well as the angle of the major axis of the elliptically polarized optical beam, when the polarization is not circular. This angle is measured with respect to a fixed frame of reference, such as a polar axis in the cross-section of the beam itself.
However, it is not always possible to do a complete analysis of the beam at a particular point in the optics system, i.e., the point of-interest, due, for example, to space constraints or because of the beam power at the point of interest. But if the beam is, instead, analyzed at a later point along the beam path, the phase or degree of polarization and the angle of the major axis of the beam may have become corrupted by the optics disposed along the beam path between the point of interest and the actual measurement point. That is, the actual measurements made on the beam at a different point may not be accurately reflective of the status of the beam at the point of interest.
It would, therefore, be desirable to provide a process and an apparatus for carrying out such measurements which would include provision for correcting or calibrating for such changes in the polarization of the beam which occur between the point of interest and the actual measurement point.